This invention relates generally to a system for tracking a boundary on a surface, and in particular to an optical tracker which automatically tracks the boundary. Before the advent of automatic tracking devices, processes requiring tracking, such as welding, cutting, applying glue or sealant, have been performed manually. Performing such processes by hand has several deficiencies. First, it requires a high degree of operator skill to manually track a seam, an edge or other types of boundaries. This level of skill is not always available. Second, even a skilled operator cannot track perfectly an irregularly shaped boundary.
Because of these and other deficiencies in manual tracking, automatic tracking equipment has been developed such as the tracking devices disclosed in U.S. Pat. Nos. 3,737,614; 4,040,557 and 4,296,306. None of such tracking devices, however, are entirely satisfactory for tracking irregular boundaries.